Those skilled in the art of bracelet manufacture, particularly for wristwatches, know that the diameter of the human wrist varies as a function of the ambient temperature and the user's physical activity. During the hot season and/or during significant physical activity by the user, the diameter of the wrist increases whereas during the cold season and/or the absence of any physical activity, the diameter decreases. The need to be able to adjust the length of the bracelet to fit it to these differences in diameter can thus be understood, if one wishes to prevent, depending upon the circumstances, the bracelet being too loose around the wrist or gripping the wearer's wrist in an uncomfortable manner.
While leather straps with a tongue and buckle generally have enough holes to be fitted sufficiently finely around the wrist, bracelets with hinged links are adjusted in length by adding or removing a link from the chain of which they are formed. In addition to the fact that the fineness of the length adjustment is limited to the length of one link, this adjustment operation still has the drawback of requiring the intervention of a specialist.
Various systems have been proposed to date to try to overcome this problem. One can cite for example CH Patent No. 669 501 and FR Patent No. 2 058 819, which propose fine adjustment systems for a bracelet. However, these systems are all integrated in a clasp of the type with an unfolding buckle or strips and utilise complicated and thus expensive devices that are not easy to use.
In order to overcome these drawbacks, EP Patent No. 0737 427 proposed a link that could be adjusted in length independently of a clasp and could thus be placed anywhere in a bracelet with links. According to this Patent, the adjustable link includes a cap into which a base slides and a spring push-button mechanism to enable the link to extend to several different lengths. The push buttons each have one end which projects onto the lateral faces of the link and an opposite end provided with a notch cooperating with the teeth of two racks facing each other and provided in the cap. U.S. Pat. No. 5,749,128 also describes a similar type of system integrated in a clasp with unfolding strips.
Although this adjustable link and clasp allow satisfactory adjustment of the length of a bracelet in which they are integrated, the control push buttons are visible from the exterior and are detrimental to the general appearance of the bracelet in which they are integrated. Moreover, these adjustment mechanisms respectively include a large number of parts that makes them complex and expensive to implement.
EP Patent No. 819 391 further discloses a device for adjusting the length of a bracelet fitted with a clasp with unfolding strips wherein the length is adjusted by means of an adjusting link have two articulation pins respectively connected to the cap of the clasp and to an end link of the bracelet. The adjusting link can pivot in relation to the pin thereof connected to the cap of the clasp to allow the pin thereof connected to the end link to pass on either side of the pin connected to the cap to define two determined lengths. The end link connected to the adjusting link has a particular shape which, when the adjusting link is in the short length position, enables it to be locked onto the adjusting link in a resilient manner. According to this device, the distance between the two articulation pins of the adjusting link determines the gap between the short length and the long length, this gap being equal to twice said distance. The choice of this length-adjusting gap is thus limited in practice by construction restrictions of the adjusting link that cannot be less than 5 mm. Moreover, this device has the drawback of only providing a choice of two determined lengths.
CH Patent No. 667 979 discloses and shows a clasp with unfolding strips wherein the adjusting link is hinged on the cap of the clasp via a connecting rod whose secondary articulation pin is slidably mounted on the adjusting link. However, the locking device disclosed in this Patent includes a relatively complex and cumbersome pusher mechanism, which is detrimental to the aesthetic appearance of the bracelet.
It is thus a main object of the present invention to overcome the drawbacks of the aforementioned prior art by furnishing a device for adjusting the length of a bracelet that allows a choice as to the spacing of the bracelet length adjustment which is independent of the distance between the articulation pins of the adjusting link on the base plate. This adjustment device must also be compact to be able to be easily integrated in a bracelet link or in a clasp with unfolding strips.
It is also an object of the present invention to furnish a device for adjusting the length of a bracelet that can be used simply by the user without using any tools.
It is also an object of the present invention to furnish a device for adjusting the length of a bracelet that is of simple, reliable and inexpensive construction.